I have several HDD of 2TB and 3TB, all of them aren't connected, I only use them once in a while (usually), when I want to connect one of them I use an external enclosure and it works fine, but yesterday and about two months ago two of my 3TB drives just weren't more recognised, I formated them and now they're OK and work fine, but I loosed all the data that were in there, I did try to recover the data but the names of the files were 01, 02, 03, etc and the name of the files were very important.

Until now not one of the 2TB drives fail, only two 3TB, could the problem be in the controller of the external enclosure? Is it possible that it only "works better" with 2TB?

I just buyed an external HD (3TB) and now I'm using this controller with the 3TB HDs and the old controller with the 2TB drives.

do a deep scan, in the options there is a setting to find file paths aswell.

3TB drives are a bit of a nightmare, not everything is compatable with them, it might have been down to the actual hardware inside the enclosure you were using not being comatable with more than 2TB, slightly over it. operating systems also have an issue with anything over 2TB, it's a hardware and software issue (motherboards bios sometimes need to be updated)

the problem might also have been caused by you removing the drive whist it was writing, or just a random error that caused the drive to be unreadable, this can sometimes happen with driver issues.

i have a external 2TB on a seperate USB 3.0 expansion card, and it will come up with a simular problem, will request formatting, sometimes show no files and sometimes only folders. this is caused by a faulty USB cable and poor drivers.

some programs are better than others, i've tried a few, some you have to pay for like GetDataBackNTFS (nto sure if there is a free version) but Recuva is just as good and should get the names and directories the files were in back as well.

have you ever thought of using a hot swap bay? might be better than enclosures.

do a deep scan, in the options there is a setting to find file paths aswell.

3TB drives are a bit of a nightmare, not everything is compatable with them, it might have been down to the actual hardware inside the enclosure you were using not being comatable with more than 2TB, slightly over it. operating systems also have an issue with anything over 2TB, it's a hardware and software issue (motherboards bios sometimes need to be updated)

the problem might also have been caused by you removing the drive whist it was writing, or just a random error that caused the drive to be unreadable, this can sometimes happen with driver issues.

i have a external 2TB on a seperate USB 3.0 expansion card, and it will come up with a simular problem, will request formatting, sometimes show no files and sometimes only folders. this is caused by a faulty USB cable and poor drivers.

This is due to the limit of the MBR partition size limit, which is 2 TB (512 multiplied by 2^32).

If you have discs that large then you should convert to GPT.

You can convert from MBR to GPT in Windows by using the command line utility called DISKPART. (WARNING! Converting will erase everything on the disk)

Updating the motherboard firmware is always recommended but converting to GPT and booting through UEFI instead of BIOS should be a high priority for anyone with a modern PC.

I convert ALL storage devices to GPT except flash memory used by portable devices, including a 32 GB memory stick and my 120 and 240 GB SSDs.

Green drives=Bad bad bad! Tons of hosting companies have issues with them. They get extra stressed from constantly being power state altered. They do that to "save energy" however they are rougher on the drives, and not very trustworthy.

Not worth loosing data over.

I would also recommend NOT using software RAID. I would use a good 3ware LSI RAID controller or don't RAID at all.